CVE-2022-48732 drm/nouveau: fix off by one in BIOS boundary checking

In the Linux kernel, the following vulnerability has been resolved:

drm/nouveau: fix off by one in BIOS boundary checking

Bounds checking when parsing init scripts embedded in the BIOS reject
access to the last byte. This causes driver initialization to fail on
Apple eMac’s with GeForce 2 MX GPUs, leaving the system with no working
console.

This is probably only seen on OpenFirmware machines like PowerPC Macs
because the BIOS image provided by OF is only the used parts of the ROM,
not a power-of-two blocks read from PCI directly so PCs always have
empty bytes at the end that are never accessed.